题解 | #反转链表#

• 三指针pre、cur、rear
• 头和尾要单独考虑：头节点指向nullptr，尾节点指向pre

class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        if(!pHead) return nullptr;
        if(!pHead->next) return pHead;
        ListNode* pre = pHead;
        ListNode* cur = pHead->next;
        ListNode* rear;
        pHead->next = nullptr;//头节点指向nullptr
        while(cur->next){
            rear = cur->next;
            cur->next = pre;
            pre = cur;
            cur = rear;
        }
        cur->next = pre;//尾节点最后再指向pre
        return cur;
    }
};